Validating an input using a simple while loop

Question

I want to validate an input to only accept 0s or 1s using a while loop. I would like to use the Boolean "OR," so while the input is not equal to 1 or 0, print an error and insist that the user reinputs the value. If it is, continue with the code so that the user can input the rest of the data.

The following codes works when a 1 is input but does not work for the second condition (in this example 0), no matter what the condition is.

number1=int(input("enter the your number)"))
while number1 !=1 or 0:
    print ("You must enter a BINARY number")
    number1=int(input("enter you first binary digit (from the right)"))

number2=int(input("enter the next (from the right)"))
while number2 !=1 or 0:
  print ("You must enter a BINARY number")
  number2=int(input("enter you second binary digit (from the right)"))

and so on...

You know the zero is simply a zero you are never testing the value for zero. — Malik Brahimi
– Malik Brahimi, Commented Mar 4, 2015 at 16:57

Malik Brahimi · Accepted Answer · 2015-03-04 16:46:54Z

1

Use this instead for multiple values:

while not number1 in (1, 0):

answered Mar 4, 2015 at 16:46

Malik Brahimi

16.8k7 gold badges46 silver badges76 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Erik Wennstrom · Accepted Answer · 2015-03-04 17:06:35Z

The other suggestions will work, but I don't think they address the issue of why what you wrote doesn't work, so I'll try to answer that.

Boolean operators like or and and are meant to go between conditions like number1 != 1 and number != 0, not between non-boolean values like 1 and 0. In English, you can write if number1 is not 1 or 0 people will understand that you mean if number1 is not 1 and number1 is not 0, but it doesn't work that way in pretty much any programming language.

So you could write if number1!=1 and number1!=0 or you could write if not (number1==1 or number1==0). Or, as others have suggested, you could write if number1 not in (0,1), which is shorter and which scales up better.

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Code:

number1 = int(raw_input("Enter your number: "))
while number1 not in (0,1):
    print("You must enter a binary number.")
    number1 = int(raw_input("Enter your number: "))

number2 = int(raw_input("Enter your second number: "))
while number2 not in (0,1):
    print("You must enter a binary number")
    number2 = int(raw_input("Enter your second number: "))

print(number1, number2)

Output:

Enter your number: 3

You must enter a binary number.

Enter your number: 1

Enter your second number: 7

You must enter a binary number

Enter your second number: 0

(1, 0)

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Mar 4, 2015 at 16:59

Stian OK

6666 silver badges14 bronze badges

2 Comments

Shawn Gordon Over a year ago

Recursion is usually suggested against - though it works, it can cause an error after too many inputs

johny why Over a year ago

Redundant statements is bad form. Your input statements are redundant.

Collectives™ on Stack Overflow

Validating an input using a simple while loop

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related